A conventional heating fan generally includes a fan unit and an electrothermal strap which generate heat when electric current passes through the electrothermal strap so that the fan unit delivers the hot air from the electrothermal strap to the users.
A convention heating fan known to applicant is disclosed in FIGS. 1 to 3, and includes a rack 1 and multiple boards 2 are connected to the rack 1, wherein the rack 1 includes a circular base 102 and multiple arms 104 extend radially from the base 102. The boards 2 each are made of thermal insulation material and connected to the arms 104 by rivets which are not shown. Each board 2 has multiple separation members 204 extending therefrom so as to define positioning recesses 202 between the separation members 204. The electrothermal strap 3 is engaged with the positioning recesses 202 of the boards 2.
When connecting the boards 2 to the arms 104, the assemblers use proper tools to rivet the boards 2. However, due to the narrow gap between the arms 104, only the wider gaps between the arms 104 allows the tools to work to rivet the boards 2, the users cannot reach the tools toward the base 102. Special tools have to be used manually and the tools can easily touch the boards 2 located around and the thermal insulation material is easily broken. This restricts the efficiency of assembly of the products.
On the other hand, when the rack 1 with electrothermal straps are installed to the case of the heat or thermal fans, the boards 2 are often broken because of impact. When the separation members 204 are broken, the two adjacent electrothermal straps are easily in contact with each other and cause circuit short. If the separation members 204 are broken, the boards 2 have to be replaced, so that the users have to remove the rivets on the arms 104 and the removal of the rivets can damage the boards 2 or the electrothermal straps. It is experienced that the way that the boards 2 are connected to the arms 104 by rivets is not convenient for maintenance. Therefore, once there are some boards 2 damaged, the whole rack 1 is replaced and this wastes material and increases the cost.
The conventional rack 1 can only wrapped with one electrothermal strap in two layers, however, in order to keep the safety gaps between the electrothermal straps, the density of the electrothermal straps is limited. If a higher thermal effect is required, the size of the heat or thermal fan has to be increased and a huge size heat or thermal fan is not welcomed in the market.
The present invention intends to provide a positioning rack for connecting the electrothermal straps, wherein the boards are engaged with the arms on the rack without use of rivets.